Capceville Y, Baltz T, Deregnaucourt C, Keller A M
Exp Cell Res. 1986 Nov;167(1):75-86. doi: 10.1016/0014-4827(86)90205-3.
The surface antigens (SAgs) of Paramecium and the variant surface antigens (VSGs) of Trypanosoma can be purified in two distinct molecular forms: a soluble form (solubilized in dilute ethanolic solution in the case of Paramecium, or in water for Trypanosoma) and a membranal form, amphiphile (solubilized in SDS). In trypanosomes, the enzymatic conversion of the membrane form into the soluble form is accompanied by the unmasking of a particular immunological determinant, called cross-reacting determinant (CRD), which is located in the COOH-terminal phospho-ethanolamine glycopeptide. We demonstrate immunological homologies between Paramecium SAgs and Trypanosoma VSGs. A determinant corresponding to the CRD of VSGs is borne by the ethanol-soluble form of the SAgs and by two cross-reacting light chains also present in ethanolic cellular extracts (together with the soluble form), and not by the membranal form of SAgs. Furthermore, we show that the membranal form of Paramecium SAgs can be converted into soluble form and that this enzymatic conversion also yields cross-reacting light chains. We also demonstrate that the membranal form is the physiological form in paramecia stably expressing a given SAg.
草履虫的表面抗原（SAgs）和锥虫的可变表面抗原（VSGs）可以以两种不同的分子形式纯化：一种可溶形式（在草履虫中可溶解于稀乙醇溶液，在锥虫中可溶解于水）和一种膜形式，两亲性（可溶解于SDS）。在锥虫中，膜形式向可溶形式的酶促转化伴随着一种特定免疫决定簇的暴露，称为交叉反应决定簇（CRD），它位于COOH末端磷酸乙醇胺糖肽中。我们证明了草履虫SAgs和锥虫VSGs之间的免疫同源性。与VSGs的CRD相对应的决定簇由SAgs的乙醇可溶形式以及乙醇细胞提取物中也存在的两条交叉反应轻链（与可溶形式一起）携带，而不由SAgs的膜形式携带。此外，我们表明草履虫SAgs的膜形式可以转化为可溶形式，并且这种酶促转化也产生交叉反应轻链。我们还证明膜形式是稳定表达给定SAgs的草履虫中的生理形式。
